Week 9 Temporal Mandibular Joint (TMJ)
MAIN STRUCTURES OF TMJ = Synovial Joint
1. Two Bones
Upper = temporal bone
 Articular fossa
 Articular eminence
Lower = mandible
 Condyle
2. Joint capsule
 completely encloses TMJ
Superiorly: wraps around temporal bone (eminence and fossa)
Inferiorly: wraps around neck of condyle
3. synovial membrane:
 Lines inner joint capsule
 Secretes synovial fluid within capsule
 Lubricates the joint
4. Articular disc (meniscus or joint disc)
 Thin, oval plate of fibrocartilage
 Lies between condyle of mandible and temporal bone
 Undersurface = concave to accommodate head of the condyle
 Acts as a cushion between the bones
 Disc divides joint into upper/lower cavities
 Each cavity has a synovial membrane that secrets synovial fluid
Anterior Attachment:
o Lateral and medial poles of condyles
o Not attached anteriorly to temporal bone
o Indirectly attached by joint capsule
Posterior Attachment:
o Upper disc = attached to temporal bone - postglenoid process
o Lower disc = attached to neck of condyle
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5. Reinforcing ligaments
 Fibrous tissue connecting opposing bones
There are three pairs associated with the TMJ:
Ligament Name
1. Temporomandibular
Point of Attachment
Function
Anterior: Lateral Wall
AKA lateral Ligament
Superior: zygomatic arch
Prevents lateral & posterior
displacement
Inferior: Lateral posterior neck of the
condyles
2. Sphenomandibular
Superior: sphenoid bone
AKA medial Ligament
Inferior: Near mandibular foramen
3. Stylomandibular
Superior: styloid process
AKA posterior Ligament
Inferior: Angle of Mandible
Helps maintain same amount of
tension during opening and
closing
Limits anterior movement
Movement of the Temporomandibular Joint (TMJ)
TMJ makes it possible for the mandible to move
Types of Movement =





Upward = elevation
Downward = depression
Forward = protrusion
Backward = retraction
Side to side = lateral
Resting Position:
 When TMJ is resting teeth are not touching
 Freeway space = 2-4 mm between opposing teeth
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Why?
 Places masticatory muscles at rest
 Permits free-way space to exist between teeth but lips are touching
 Mandibular condyles are positioned posterior the articular eminence
 Disc is positioned between the two bones
TMJ Movements during speech/mastication
Opening:
 Depression
 Protrusion
Closing =
 Retraction
 Elevation
Two Movements of the TMJ:
1. Hinge or rotation = Ginglymus movement
 Depression
 Elevation
 This phase of opening is occurring only in lower synovial cavity of joint
 Between disc and head of condyle
 Condylar head rotates around a point on undersurface of articular disc
 Several muscles are involved
 Normal rotation occurs until upper and lower teeth are 20 mm away from each other
2. gliding = arthrodial motion
 Protrusion
 Retraction
 Occurs as disc slides along articular eminence
 Involves mainly upper synovial cavity of joint
 Condyle and articular disc “glide” forward and downward along articular eminence
Opening and Closing =
Need:
 Rotation movement
 Gliding movement
 Left and right TMJ need to work together
 Muscles are also involved
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Major Muscles of Mastication (A,B,C are the three muscles that close the mandible)
Muscle Name
A) masseter
Origin
Zygomatic Arch
Insertion
External Angle of
mandible
Action
Elevates mandible
(Closes the jaw)
B) temporalis
Temporal Fossa
Coronoid process
of mandible
Elevates and retracts
mandible
C) medial
Pterygoid
Pterygoid Process
Internal Angle of
mandible
Closes (elevates) mandible
D) lateral
Pterygoid
Greater wing of
sphenoid bone
Near a fossa on the
condyle
Protrusion
Slight depression
Lateral movement
INSERTION POINTS FOR THE MUSCLES OF MASTICATION
# 4 = Medial pterygoid # 3 = Internal pterygoid
# 1 = Temporalis
# 2 = Masseter
Summary of Muscles of Mastication
Elevating the mandible when closing:
 Masseter
 Temporalis
 Medial pterygoid
Depressing the mandible when opening:
 Lateral pterygoid
 Anterior suprahyoid (not discussed)
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Lateral Deviation





Shifting of mandible from side to side
Involves both rotational and gliding movements of opposing TMJ
One disc plus condyle glide forward and medially on articular eminence
The other disc and condyle will remain stable
Also need is contraction of one lateral pterygoid muscle on protruding side
Temporomandibular Disorder (TMD)
Disease of one or both TMJ
Symptoms:
 Chronic joint tenderness
 Muscle spasms
 Headaches
 Pain:
 In face, neck or ear
 When chewing
 May have limited opening or deviation
Palpation, MRI and/or radiographs aid in diagnosis
Causes:
 Usually stress related
 Accidents involving injury to joint
 Diseases
 Malocclusions = may need orthodontics to correct
Crepitus:
 Sounds of popping / clicking
 Occurs when condyle rotates and translates forward down articular eminence
 If disc becomes displaced mandible will “click”
Correction =
 May need physical therapy or
 Plastic splint = like a night guard
Subluxation:
 Jaw locks
 Condyle is displaced too anteriorly over articular eminence
 Does not return to its normal position
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Correction =
 Place gauze around thumb
 Place thumbs along occlusal of mand. teeth
 Gently press down/posterior
Trismus:
 Limited ability to open
 Loss of elasticity of muscles of mastication or TMJ ligaments
Correction:
 Exercise at least 3x/day
 Open/close 20 times without causing pain
Bruxism = “grinding teeth”
 May be caused by TMD
 Stress or tension
Inflammation of the joint = arthritis
 Cortisone may help with pain
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Vertebral Column:





“spine”
Formed of 26 irregular bones
Extends from skull to pelvis
Bones are held together by ligaments to provide a somewhat flexible curved structure.
Each vertebra is separated by fibrocartilage called intervertebral Discs
Purpose:
 Spaces vertebrae
 Absorbs vibration as we walk
 Compresses to allow bending of torso
Younger person:
 Discs have high water content
 Spongy and compressible
As we age:
 Water content will decrease
 Discs are harder
 Less compressible
The vertebrae are divided into groups by location in this manner:
Name of Vertebrae Group
# on
diagram
Position
Cervical (neck)
1
First 7 vertebrae (C1 – C7)
Thoracic (chest)
2
Next 12 vertebrae (T1 – T12)
Lumbar (small of back)
3
Next 5 vertebrae (L1 – L5)
sacrum (Posterior of pelvis)
4
1 Vertebrae (which is actually 5 fused vertebrae)
Coccyx “tailbone” (End of
column)
5
1 Vertebrae (which is actually 4 fused vertebrae)
Total Vertebrae = 26
First Cervical Vertebrae = C1 = atlas #6
Second Cervical Vertebrae = C2 = Axis #7
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Parts of Typical Vertebrae
Body = 1
Lamina = 3
Spinous process = 4
Transverse processes = 2
Vertebral foramen = 5
Orientation of the spinous process in the vertebrae column is (anterior/posterior) = posterior
The vertebrae have a basic structure but there are some modifications to their shape in
different areas of the spinal column.
BODY:
Becomes larger as move down = supports more weight
SPINOUS PROCESS:
Becomes thinner but longer as move down
TRANSVERSE PROCESS:
Becomes wider as move down = supports more weight
FORAMEN:
Becomes larger as move up = spinal cord is larger near
brain
C1 = atlas = ring
C2 = axis has tooth-like projection upward called a dens
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